1. Field of the Invention
This invention relates to a thermally conductive grease-like material.
2. Description of the Prior Art
Thermally conductive greases are well known in the art and are useful for sealing between two bodies wherein it is desirable to transfer heat between the two bodies. These greases may also be used to improve thermal conductivity between two contacting surfaces wherein a layer of grease between the surfaces fills in any air spaces. For low temperature applications these greases typically include hydrocarbon or parafin type oils filled, for example, with aluminum oxide, aluminum hydrate, silica, carbon or graphite. For temperatures greater than about 250.degree. F silicon oil base greases are often used in place of the hydrocarbon parafin base greases.
None of these prior art thermally conductive greases are entirely suitable in the environment of a phosphoric acid fuel cell or stack of fuel cells wherein temperatures may exceed 250.degree. F. Greases of parafin or silicon oils typically are volatilized, oxidized or react with H.sub.3 PO.sub.4 at cell operation conditions. The silicon oil base greases tend to volatilize at the higher temperatures, with a resultant loss in thermal conductivity due to void formation in the grease. As the grease dries, it cracks, resulting in a loss of surface contact which defeats the purpose of the grease, namely, to provide high thermal conductivity between the adjacent components.